Employment among lower-income men has declined by 11 percent since 1980 and has remained flat among lower-income women. Men and women in the top and middle of the income distribution, on the other hand, have been working as much or more since 1980, creating a growing “work gap” in labor market income between haves and have-nots.

This paper simulates the effect of five labor market interventions (higher high school graduation rate, minimum wage increases, maintaining full employment, seeing all household heads work full time, and virtual marriages between single mothers and unattached men) on the average incomes of the poorest one-third of American households. They find that the most effective way to increase average incomes of the poorest Americans would be for household heads to work full time, whereas the least effective intervention would be increasing education.

In terms of actual impact on incomes, the simulation of all household heads working full time at their expected wage increased average household earnings by 54 percent from a baseline of $12,415 to $19,163. The research also suggests that even if all household heads worked just some—at expected wages or hours—average earnings would still increase by 16 percent.

The least effective simulation was increasing the high school graduation rate to 90 percent and having half of those “newly” graduated go on to receive some form of post-secondary education. The authors note that the low impact of increasing education on mobility is likely because only one in six of bottom-third adults live in a household in which someone gains a high school degree via the intervention.

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Because single parents are disproportionately represented among low-income families, Sawhill and coauthors also explored the impact of adding a second earner to single-parent families through a simulation that pairs low-income, single-mother household heads with demographically similar but unrelated men. That simulation increased the average household earnings of the bottom-third only modestly, by $508, or about 4 percent.

Efforts to increase employment among heads of the poorest households must take into consideration why those household heads aren’t working, they note. According to data from the 2015 Census, the most cited reason for women not working is “taking care of home and family” and for men it is being “ill or disabled.”